The original description of Crossocheilus oblongus by Kuhl & Van Hasselt in Van Hasselt (1823) is rather concise.
Crossocheilus Nob. is een aan Leuciscus verwant genus, onderscheidt zich door eene naar onderen gerig- te mondopening, in den vorm van een paralelogram; de teekening draagt den naam van Oblongus Nob.
No details on coloration are provided. It is by far not clear whether or not the interpretation by Bleeker in his Atlas is correct. The images of the alleged holotype/syntype RMNH 2640 bring little inspiration concerning coloration too. Lateral stripe starting at the opercle and containing lateral line, and a black blotch on caudal peduncle similar to Crossocheilus reticulatus are visible. The colour pattern of RMNH D1755, the holotype/lectotype designated by Alfred according to Tan & Kottelat, and RMNH D1756 shows lateral stripe ending on the caudal peduncle. No traces of black pigment are visible on caudal fin.
The original drawing mentioned in the description was in the possession of Bleeker and is missing now. The watercolour replica of it by Sophie D. was published in Roberts, 1993. It clearly shows a lateral stripe starting at the snout, contradicting the information in Bleeker, and ending at the caudal base. No black pigment in caudal fin is depicted.
Labeo oblongus is usually cited as a synonym of Crossocheilus oblongus. But its description by Valenciennes in Cuvier & Valenciennes (1842) is rather surprising.
Le fond général de la couleur est bleu, foncé sur le dos et s'éclaircissant sous le ventre; la dor- sale, l'anale et la caudale sont jaunes; les pectorales sont orangées; les ventrales plus pâles. J'ai fait une description à Leyde sur un poisson long de cinq pouces; mais il paraît que l'espèce atteint à deux pieds.
Nevertheless, it corresponds to the original colour drawing by Keultjes, Kuhl and Van Hasselt. As reported by Roberts, Valenciennes visited Leiden in 1824 and 1827. In 1827, he studied marine species. At the same time Sophie made the replica. No black pigment in caudal fin is mentioned in 1 year, less likely 4 years, old specimen. In contrast, the 79 years old holotype of Epalzeorhynchos siamense caught 1928 and photographed 2007 had caudal fin clearly black pigmented along the midline. The holotype of Labeo oblongus was 5 French inches long, approximately 135 mm. In contrast, the holotype or syntype of Crossocheilus oblongus designated by Richards has approximately 75 mm SL, in my guess about 100 mm TL. The specimen RMNH D1755 designated by Alfred is better lectotype.
It is by far not certain that the alcohol-preserved RMNH 2640 and the stuffed RMNH D1755 are conspecific.
Bleeker alleged the following details in 1853. colore corpore superne coerulescente, inferne margaritaceo; fascia cephalo-cau- dali profunde coerulea; pinnis flavescentibus vel roseis.
No black pigment in caudal fin is mentioned.
I wonder how Javanese Crossocheilus oblongus looks like.
http://repository.naturalis.nl/document/149052#page=53
Caudal fin of the lectotype RMNH-D1755 depicted in
http://www.math.muni.cz/~niederle/crossocheilus_siamensis_page.html
In the image originally by Van Hasselt, rostral cap does not cover upper lip. I wonder whether rostral cap covers upper lip in RMNH D1755.
Confer interesting images
http://www.math.muni.cz/~niederle/crossoanglicky.html#bif
Nicolas Hubert published the attached photographs of Crossocheilus specimens from Indonesia.
http://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=495805
http://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=517866
The photographs are under CC license.
CreativeCommons Attribution Non-Commercial Share-Alike (2016)
https://creativecommons.org/licenses/by-nc-sa/3.0/
Which is the genuine one.
Their localities remain unknown of course. I would greatly appreciate if the author would divulge the localities at least geographically.
Click on the link to the picture below.
I have rewritten the original handwritten descriptions of the genus Crossocheilos and of the species Crossocheilos oblongus.
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